Context fetch procedure for inactive direct data transmission

ABSTRACT

A method and apparatus of a device that communicates data between a user equipment (UE) device and a base station when the user equipment is in the inactive state is described. In some embodiments, the last serving base station of the UE and the new base station of the UE coordinate with each other to complete the transfer of data while the UE is in the inactive state.

The present application is a continuation of U.S. application Ser. No.17/598,240, filed Oct. 14, 2021, which is the national phase ofInternational Application No. PCT/CN2020/117809, filed on Sep. 25, 2020,and the disclosures of which are hereby incorporated herein by referencein its entirety.

FIELD OF INVENTION

Embodiments of invention relate generally to wireless technology andmore particularly to handling direct data transmission with userequipment (UE) when in an inactive state.

BACKGROUND

In 5G New Radio (NR), a user equipment (UE) can be in one of threestates: CONNECTED, INACTIVE, and IDLE. The CONNECTED state allows forfull data transmission between the UE and a base station (BS) and thecore network (CN). The IDLE state is a power saving state where data isnot exchanged. The INACTICVE state for a UE is a suspend state thatallows for the UE to return to the CONNECTED state more quickly than ifthe UE is in the IDLE state.

In 5G NR, in order for a UE to transition to the CONNECTED state inorder to allow for full data transmission, the UE would perform a RadioResource Control (RRC) Resume procedure. The RRC Resume procedure takestime to complete. Thus, there is a delay that is necessary to completethe RRC Resume procedure between the time data for transfer arrivesuntil the data can be transmitted. Normally, such a delay is notconsidered problematic when the UE is going to be involved intransferring a large amount of data. However, if the amount of data issmall, such that a UE would quickly return to an inactive state soonafter performing the smaller data transfer, then the delay in completingthe RRC Resume procedure may be considered unreasonable.

Recently, 5G NR specified that a UE can transfer smaller amounts of datawhile in the inactive state. This is advantageous in that it avoids thedelay the UE incurs by completing the RRC Resume procedure. However,there is no specification in 5G NR as to how such transfers are to behandled by the network.

SUMMARY OF THE DESCRIPTION

A method and apparatus of a device that communicates data between a userequipment (UE) device and a base station (BS) when the user equipment isin the inactive state (e.g., a Radio Resource Control (RRC) inactive(RRC_INACTIVE) state) is described.

In some embodiments, the last serving base station of the UE and the newbase station of the UE coordinate with each other to complete thetransfer of data while the UE is in the inactive state. In someembodiments, a last serving base station both a message requesting UEcontext and user plane uplink data from a new base station of the UE,where the user plane uplink data is sent from the UE to the last servingbase station while the UE was in the inactive state, and forwards theuser plane uplink data to the core network (CN) on behalf of the UE.

In some embodiments, a new base station for the UE receives user planeuplink data transmitted from a user equipment (UE) while the UE was inthe inactive (RRC_INACTIVE) state and sends both a message to the lastserving base station to request UE context along with the user planeuplink data, so that the last serving base station can forward the datato the CN.

In some embodiments, the last serving base station sending a message tothe UE to configure the UE in the inactive state and sends the UEcontext to one or more other base stations that can potentially act asthe new base station for the UE. This facilitates the transfer ofresponsibility from the last serving base station to a new base stationto enable completion of the data transfer with the UE while the UE is inan inactive state.

In some embodiments, the new base station receives a UE context that thelast serving base station sends to one or more other base stations thatcan potentially act as the new base station for a UE. Thereafter, thenew base station receives user plane uplink data transmitted from the UEwhile the UE was in the inactive state and operates as an anchor nodefor the UE in response to receiving the user plane uplink data from theUE.

Other methods and apparatuses are also described.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example and notlimitation in the figures of the accompanying drawings in which likereferences indicate similar elements.

FIG. 1 illustrates an example wireless communication system according tosome embodiments.

FIG. 2 illustrates a base station (BS) in communication with a userequipment (UE) device according to some embodiments.

FIG. 3 illustrates an example block diagram of a UE according to someembodiments.

FIG. 4 illustrates an example block diagram of a BS according to someembodiments.

FIG. 5 illustrates an example block diagram of cellular communicationcircuitry, according to some embodiments.

FIG. 6 is an illustration of some embodiments of a UE switch from aninactive state to a connected state.

FIG. 7A is an illustration of some embodiments of a is timeline of UEswitch from an inactive state to a connected state.

FIG. 7B is an illustration of some embodiments of a is timeline of UE tocommunicate data in an inactive state.

FIG. 8 is an illustration of some embodiments of communicating data witha UE in the inactive state and the last served gNodeB (gNB) remains theanchor node.

FIG. 9 is an illustration of some embodiments of communicating data witha UE in the inactive state and the new gNB becomes the anchor node.

FIG. 10 is an illustration of some embodiments of communicating datawith a UE in the inactive state and the new gNB temporarily becomes theanchor node.

FIG. 11A is a flow diagram of one embodiment of a process performed by alast serving gNB for handling a user plane uplink data sent from a UEwhile the UE is in the RRC_INACTIVE state.

FIG. 11B is a flow diagram of one embodiment of a process performed by anew gNB for handling a user plane uplink data sent from a UE while theUE is in the RRC_INACTIVE state.

FIG. 12A is a flow diagram of another embodiment of a process performedby a last serving gNB for handling a user plane uplink data sent from aUE while the UE is in the RRC_INACTIVE state.

FIG. 12B is a flow diagram of another embodiment of a process performedby a new gNB for handling a user plane uplink data sent from a UE whilethe UE is in the RRC_INACTIVE state.

FIG. 13A is a flow diagram of yet another embodiment of a processperformed by a last serving gNB for handling a user plane uplink datasent from a UE while the UE is in the RRC_INACTIVE state.

FIG. 13B is a flow diagram of yet another embodiment of a processperformed by a new gNB for handling a user plane uplink data sent from aUE while the UE is in the RRC_INACTIVE state.

FIGS. 14A and 14B illustrate some embodiments of communicating data witha UE in the inactive state, where a last served gNB sends a UE contextto another gNB prior to receiving data.

FIG. 15A is a flow diagram of another embodiment of a process performedby a last serving gNB for handling sends a UE context to another gNBprior to receiving user plane uplink data from a UE while the UE is inthe RRC_INACTIVE state.

FIG. 15B is a flow diagram of one embodiment of a process for handlingnew downlink data from the CN that is sent to the last serving gNB priorto the UE sending data to the new gNB while the UE is in theRRC_INACTIVE state.

FIG. 16A is a flow diagram of yet another embodiment of a processperformed by a last serving gNB for handling sends a UE context toanother gNB prior to receiving user plane uplink data from a UE whilethe UE is in the RRC_INACTIVE state.

FIG. 16B is a flow diagram of another embodiment of a process forhandling new downlink data from the CN that is sent to the last servinggNB prior to the UE sending data to the new gNB while the UE is in theRRC_INACTIVE state.

DETAILED DESCRIPTION

A method and apparatus of a device that communicates data between a userequipment (UE) device and a base station when the user equipment is inthe inactive state is described. In the following description, numerousspecific details are set forth to provide thorough explanation ofembodiments of the present invention. It will be apparent, however, toone skilled in the art, that embodiments of the present invention may bepracticed without these specific details. In other instances, well-knowncomponents, structures, and techniques have not been shown in detail inorder not to obscure the understanding of this description.

Reference in the specification to “some embodiments” or “an embodiment”means that a particular feature, structure, or characteristic describedin connection with the embodiment can be included in at least oneembodiment of the invention. The appearances of the phrase “in someembodiments” in various places in the specification do not necessarilyall refer to the same embodiment.

In the following description and claims, the terms “coupled” and“connected,” along with their derivatives, may be used. It should beunderstood that these terms are not intended as synonyms for each other.“Coupled” is used to indicate that two or more elements, which may ormay not be in direct physical or electrical contact with each other,co-operate or interact with each other. “Connected” is used to indicatethe establishment of communication between two or more elements that arecoupled with each other.

The processes depicted in the figures that follow, are performed byprocessing logic that comprises hardware (e.g., circuitry, dedicatedlogic, etc.), software (such as is run on a general-purpose computersystem or a dedicated machine), or a combination of both. Although theprocesses are described below in terms of some sequential operations, itshould be appreciated that some of the operations described may beperformed in different order. Moreover, some operations may be performedin parallel rather than sequentially.

The terms “server,” “client,” and “device” are intended to refergenerally to data processing systems rather than specifically to aparticular form factor for the server, client, and/or device.

A method and apparatus of a device that communicates data between a userequipment (UE) device and a base station (B S) when the user equipmentis in the inactive state (e.g., a Radio Resource Control (RRC) inactive(RRC_INACTIVE) state) is described. In some embodiments, the lastserving base station of the UE and the new base station of the UEcoordinate with each other to complete the transfer of data while the UEis in the inactive state. For example, in some embodiments, a lastserving base station both a message requesting UE context and user planeuplink data from a new base station of the UE, where the user planeuplink data is sent from the UE to the last serving base station whilethe UE was in the inactive state, and forwards the user plane uplinkdata to the core network (CN) on behalf of the UE.

As another example, a new base station for the UE receives user planeuplink data transmitted from a user equipment (UE) while the UE was inthe inactive (RRC_INACTIVE) state and sends both a message to the lastserving base station to request UE context along with the user planeuplink data, so that the last serving base station can forward the datato the CN.

In yet another example, the last serving base station sending a messageto the UE to configure the UE in the inactive state and sends the UEcontext to one or more other base stations that can potentially act asthe new base station for the UE. This facilitates the transfer ofresponsibility from the last serving base station to a new base stationto enable completion of the data transfer with the UE while the UE is inan inactive state.

In still yet another example, the new base station receives a UE contextthat the last serving base station sends to one or more other basestations that can potentially act as the new base station for a UE.Thereafter, the new base station receives user plane uplink datatransmitted from the UE while the UE was in the inactive state andoperates as an anchor node for the UE in response to receiving the userplane uplink data from the UE.

FIG. 1 illustrates a simplified example wireless communication system,according to some embodiments. It is noted that the system of FIG. 1 ismerely one example of a possible system, and that features of thisdisclosure may be implemented in any of various systems, as desired.

As shown, the example wireless communication system includes a basestation 102A which communicates over a transmission medium with one ormore user devices 106A, 106B, etc., through 106N. Each of the userdevices may be referred to herein as a “user equipment” (UE). Thus, theuser devices 106 are referred to as UEs or UE devices.

The base station (BS) 102A may be a base transceiver station (BTS) orcell site (a “cellular base station”) and may include hardware thatenables wireless communication with the UEs 106A through 106N.

The communication area (or coverage area) of the base station may bereferred to as a “cell.” The base station 102A and the UEs 106 may beconfigured to communicate over the transmission medium using any ofvarious radio access technologies (RATs), also referred to as wirelesscommunication technologies, or telecommunication standards, such as GSM,UMTS (associated with, for example, WCDMA or TD-SCDMA air interfaces),LTE, LTE-Advanced (LTE-A), 5G new radio (5G NR), HSPA, 3GPP2 CDMA2000(e.g., 1×RTT, 1×EV-DO, HRPD, eHRPD), etc. Note that if the base station102A is implemented in the context of LTE, it may alternately bereferred to as an ‘eNodeB’ or ‘eNB’. Note that if the base station 102Ais implemented in the context of 5G NR, it may alternately be referredto as ‘gNodeB’ or ‘gNB’.

As shown, the base station 102A may also be equipped to communicate witha network 100 (e.g., a core network of a cellular service provider, atelecommunication network such as a public switched telephone network(PSTN), and/or the Internet, among various possibilities). Thus, thebase station 102A may facilitate communication between the user devicesand/or between the user devices and the network 100. In particular, thecellular base station 102A may provide UEs 106 with varioustelecommunication capabilities, such as voice, SMS and/or data services.

Base station 102A and other similar base stations (such as base stations102B . . . 102N) operating according to the same or a different cellularcommunication standard may thus be provided as a network of cells, whichmay provide continuous or nearly continuous overlapping service to UEs106A-N and similar devices over a geographic area via one or morecellular communication standards.

Thus, while base station 102A may act as a “serving cell” for UEs 106A-Nas illustrated in FIG. 1 , each UE 106 may also be capable of receivingsignals from (and possibly within communication range of) one or moreother cells (which might be provided by base stations 102B-N and/or anyother base stations), which may be referred to as “neighboring cells”.Such cells may also be capable of facilitating communication betweenuser devices and/or between user devices and the network 100. Such cellsmay include “macro” cells, “micro” cells, “pico” cells, and/or cellswhich provide any of various other granularities of service area size.For example, base stations 102A-B illustrated in FIG. 1 might be macrocells, while base station 102N might be a micro cell. Otherconfigurations are also possible.

In some embodiments, base station 102A may be a next generation basestation, e.g., a New Radio (5G NR) base station, or “gNB”. In someembodiments, a gNB may be connected to a legacy evolved packet core(EPC) network and/or to a NR core (NRC) network. In addition, a gNB cellmay include one or more transition and reception points (TRPs). Inaddition, a UE capable of operating according to 5G NR may be connectedto one or more TRPs within one or more gNBs.

Note that a UE 106 may be capable of communicating using multiplewireless communication standards. For example, the UE 106 may beconfigured to communicate using a wireless networking (e.g., Wi-Fi)and/or peer-to-peer wireless communication protocol (e.g., Bluetooth,Wi-Fi peer-to-peer, etc.) in addition to at least one cellularcommunication protocol (e.g., GSM, UMTS (associated with, for example,WCDMA or TD-SCDMA air interfaces), LTE, LTE-A, 5G NR, HSPA, 3GPP2CDMA2000 (e.g., 1×RTT, 1×EV-DO, HRPD, eHRPD), etc.). The UE 106 may alsoor alternatively be configured to communicate using one or more globalnavigational satellite systems (GNSS, e.g., GPS or GLONASS), one or moremobile television broadcasting standards (e.g., ATSC-M/H or DVB-H),and/or any other wireless communication protocol, if desired. Othercombinations of wireless communication standards (including more thantwo wireless communication standards) are also possible.

FIG. 2 illustrates user equipment 106 (e.g., one of the devices 106Athrough 106N) in communication with a base station 102, according tosome embodiments. The UE 106 may be a device with cellular communicationcapability such as a mobile phone, a hand-held device, a computer or atablet, or virtually any type of wireless device.

The UE 106 may include a processor that is configured to execute programinstructions stored in memory. The UE 106 may perform any of the methodembodiments described herein by executing such stored instructions.Alternatively, or in addition, the UE 106 may include a programmablehardware element such as an FPGA (field-programmable gate array) that isconfigured to perform any of the method embodiments described herein, orany portion of any of the method embodiments described herein.

The UE 106 may include one or more antennas for communicating using oneor more wireless communication protocols or technologies. In someembodiments, the UE 106 may be configured to communicate using, forexample, CDMA2000 (1×RTT/1×EV-DO/HRPD/eHRPD) or LTE using a singleshared radio and/or GSM or LTE using the single shared radio. The sharedradio may couple to a single antenna, or may couple to multiple antennas(e.g., for MIMO) for performing wireless communications. In general, aradio may include any combination of a baseband processor, analog RFsignal processing circuitry (e.g., including filters, mixers,oscillators, amplifiers, etc.), or digital processing circuitry (e.g.,for digital modulation as well as other digital processing). Similarly,the radio may implement one or more receive and transmit chains usingthe aforementioned hardware. For example, the UE 106 may share one ormore parts of a receive and/or transmit chain between multiple wirelesscommunication technologies, such as those discussed above.

In some embodiments, the UE 106 may include separate transmit and/orreceive chains (e.g., including separate antennas and other radiocomponents) for each wireless communication protocol with which it isconfigured to communicate. As a further possibility, the UE 106 mayinclude one or more radios which are shared between multiple wirelesscommunication protocols, and one or more radios which are usedexclusively by a single wireless communication protocol. For example,the UE 106 might include a shared radio for communicating using eitherof LTE or 5G NR (or LTE or 1×RTT or LTE or GSM), and separate radios forcommunicating using each of Wi-Fi and Bluetooth. Other configurationsare also possible.

FIG. 3 —Block Diagram of a UE

FIG. 3 illustrates an example simplified block diagram of acommunication device 106, according to some embodiments. It is notedthat the block diagram of the communication device of FIG. 3 is only oneexample of a possible communication device. According to embodiments,communication device 106 may be a user equipment (UE) device, a mobiledevice or mobile station, a wireless device or wireless station, adesktop computer or computing device, a mobile computing device (e.g., alaptop, notebook, or portable computing device), a tablet and/or acombination of devices, among other devices. As shown, the communicationdevice 106 may include a set of components 300 configured to performcore functions. For example, this set of components may be implementedas a system on chip (SOC), which may include portions for variouspurposes. Alternatively, this set of components 300 may be implementedas separate components or groups of components for the various purposes.The set of components 300 may be coupled (e.g., communicatively;directly or indirectly) to various other circuits of the communicationdevice 106.

For example, the communication device 106 may include various types ofmemory (e.g., including NAND flash 310), an input/output interface suchas connector I/F 320 (e.g., for connecting to a computer system; dock;charging station; input devices, such as a microphone, camera, keyboard;output devices, such as speakers; etc.), the display 360, which may beintegrated with or external to the communication device 106, andcellular communication circuitry 330 such as for 5G NR, LTE, GSM, etc.,and short to medium range wireless communication circuitry 329 (e.g.,Bluetooth™ and WLAN circuitry). In some embodiments, communicationdevice 106 may include wired communication circuitry (not shown), suchas a network interface card, e.g., for Ethernet.

The cellular communication circuitry 330 may couple (e.g.,communicatively; directly or indirectly) to one or more antennas, suchas antennas 335 and 336 as shown. The short to medium range wirelesscommunication circuitry 329 may also couple (e.g., communicatively;directly or indirectly) to one or more antennas, such as antennas 337and 338 as shown. Alternatively, the short to medium range wirelesscommunication circuitry 329 may couple (e.g., communicatively; directlyor indirectly) to the antennas 335 and 336 in addition to, or insteadof, coupling (e.g., communicatively; directly or indirectly) to theantennas 337 and 338. The short to medium range wireless communicationcircuitry 329 and/or cellular communication circuitry 330 may includemultiple receive chains and/or multiple transmit chains for receivingand/or transmitting multiple spatial streams, such as in amultiple-input multiple output (MIMO) configuration.

In some embodiments, as further described below, cellular communicationcircuitry 330 may include dedicated receive chains (including and/orcoupled to, e.g., communicatively; directly or indirectly. dedicatedprocessors and/or radios) for multiple radio access technologies (RATs)(e.g., a first receive chain for LTE and a second receive chain for 5GNR). In addition, in some embodiments, cellular communication circuitry330 may include a single transmit chain that may be switched betweenradios dedicated to specific RATs. For example, a first radio may bededicated to a first RAT, e.g., LTE, and may be in communication with adedicated receive chain and a transmit chain shared with an additionalradio, e.g., a second radio that may be dedicated to a second RAT, e.g.,5G NR, and may be in communication with a dedicated receive chain andthe shared transmit chain.

The communication device 106 may also include and/or be configured foruse with one or more user interface elements. The user interfaceelements may include any of various elements, such as display 360 (whichmay be a touchscreen display), a keyboard (which may be a discretekeyboard or may be implemented as part of a touchscreen display), amouse, a microphone and/or speakers, one or more cameras, one or morebuttons, and/or any of various other elements capable of providinginformation to a user and/or receiving or interpreting user input.

The communication device 106 may further include one or more smart cards345 that include SIM (Subscriber Identity Module) functionality, such asone or more UICC(s) (Universal Integrated Circuit Card(s)) cards 345.

As shown, the SOC 300 may include processor(s) 302, which may executeprogram instructions for the communication device 106 and displaycircuitry 304, which may perform graphics processing and provide displaysignals to the display 360. The processor(s) 302 may also be coupled tomemory management unit (MMU) 340, which may be configured to receiveaddresses from the processor(s) 302 and translate those addresses tolocations in memory (e.g., memory 306, read only memory (ROM) 350, NANDflash memory 310) and/or to other circuits or devices, such as thedisplay circuitry 304, short range wireless communication circuitry 229,cellular communication circuitry 330, connector I/F 320, and/or display360. The MMU 340 may be configured to perform memory protection and pagetable translation or set up. In some embodiments, the MMU 340 may beincluded as a portion of the processor(s) 302.

As noted above, the communication device 106 may be configured tocommunicate using wireless and/or wired communication circuitry. Thecommunication device 106 may also be configured to enter and exit aninactive state (e.g., RRC_INACTIVE state) and transfer data with therest of the communication network while in the inactive state. In someembodiments, such transfers may involve user plane uplink data and/oruser plane downlink data and are facilitated by the last serving basestation and a new base station.

As described herein, the communication device 106 may include hardwareand software components for implementing the above features fordetermining a physical downlink shared channel scheduling resource for acommunications device 106 and a base station. The processor 302 of thecommunication device 106 may be configured to implement part or all ofthe features described herein, e.g., by executing program instructionsstored on a memory medium (e.g., a non-transitory computer-readablememory medium). Alternatively (or in addition), processor 302 may beconfigured as a programmable hardware element, such as an FPGA (FieldProgrammable Gate Array), or as an ASIC (Application Specific IntegratedCircuit). Alternatively (or in addition) the processor 302 of thecommunication device 106, in conjunction with one or more of the othercomponents 300, 304, 306, 310, 320, 329, 330, 340, 345, 350, 360 may beconfigured to implement part or all of the features described herein.

In addition, as described herein, processor 302 may include one or moreprocessing elements. Thus, processor 302 may include one or moreintegrated circuits (ICs) that are configured to perform the functionsof processor 302. In addition, each integrated circuit may includecircuitry (e.g., first circuitry, second circuitry, etc.) configured toperform the functions of processor(s) 302.

Further, as described herein, cellular communication circuitry 330 andshort range wireless communication circuitry 329 may each include one ormore processing elements. In other words, one or more processingelements may be included in cellular communication circuitry 330 and,similarly, one or more processing elements may be included in shortrange wireless communication circuitry 329. Thus, cellular communicationcircuitry 330 may include one or more integrated circuits (ICs) that areconfigured to perform the functions of cellular communication circuitry330. In addition, each integrated circuit may include circuitry (e.g.,first circuitry, second circuitry, etc.) configured to perform thefunctions of cellular communication circuitry 230. Similarly, the shortrange wireless communication circuitry 329 may include one or more ICsthat are configured to perform the functions of short range wirelesscommunication circuitry 32. In addition, each integrated circuit mayinclude circuitry (e.g., first circuitry, second circuitry, etc.)configured to perform the functions of short range wirelesscommunication circuitry 329.

FIG. 4 —Block Diagram of a Base Station

FIG. 4 illustrates an example block diagram of a base station 102,according to some embodiments. It is noted that the base station of FIG.4 is merely one example of a possible base station. As shown, the basestation 102 may include processor(s) 404 which may execute programinstructions for the base station 102. The processor(s) 404 may also becoupled to memory management unit (MMU) 440, which may be configured toreceive addresses from the processor(s) 404 and translate thoseaddresses to locations in memory (e.g., memory 460 and read only memory(ROM) 450) or to other circuits or devices.

The base station 102 may include at least one network port 470. Thenetwork port 470 may be configured to couple to a telephone network andprovide a plurality of devices, such as UE devices 106, access to thetelephone network as described above in FIGS. 1 and 2 .

The network port 470 (or an additional network port) may also oralternatively be configured to couple to a cellular network, e.g., acore network of a cellular service provider. The core network mayprovide mobility related services and/or other services to a pluralityof devices, such as UE devices 106. In some cases, the network port 470may couple to a telephone network via the core network, and/or the corenetwork may provide a telephone network (e.g., among other UE devicesserviced by the cellular service provider).

In some embodiments, base station 102 may be a next generation basestation, e.g., a 5G New Radio (5G NR) base station, or “gNB”. In suchembodiments, base station 102 may be connected to a legacy evolvedpacket core (EPC) network and/or to a NR core (NRC) network. Inaddition, base station 102 may be considered a 5G NR cell and mayinclude one or more transition and reception points (TRPs). In addition,a UE capable of operating according to 5G NR may be connected to one ormore TRPs within one or more gNB s.

The base station 102 may include at least one antenna 434, and possiblymultiple antennas. The at least one antenna 434 may be configured tooperate as a wireless transceiver and may be further configured tocommunicate with UE devices 106 via radio 430. The antenna 434communicates with the radio 430 via communication chain 432.Communication chain 432 may be a receive chain, a transmit chain orboth. The radio 430 may be configured to communicate via variouswireless communication standards, including, but not limited to, 5G NR,LTE, LTE-A, GSM, UMTS, CDMA2000, Wi-Fi, etc.

The base station 102 may be configured to communicate wirelessly usingmultiple wireless communication standards. In some instances, the basestation 102 may include multiple radios, which may enable the basestation 102 to communicate according to multiple wireless communicationtechnologies. For example, as one possibility, the base station 102 mayinclude an LTE radio for performing communication according to LTE aswell as a 5G NR radio for performing communication according to 5G NR.In such a case, the base station 102 may be capable of operating as bothan LTE base station and a 5G NR base station. As another possibility,the base station 102 may include a multi-mode radio which is capable ofperforming communications according to any of multiple wirelesscommunication technologies (e.g., 5G NR and Wi-Fi, LTE and Wi-Fi, LTEand UMTS, LTE and CDMA2000, UMTS and GSM, etc.).

As described further subsequently herein, the BS 102 may includehardware and software components for implementing or supportingimplementation of features described herein. The processor 404 of thebase station 102 may be configured to implement or supportimplementation of part or all of the methods described herein, e.g., byexecuting program instructions stored on a memory medium (e.g., anon-transitory computer-readable memory medium). Alternatively, theprocessor 404 may be configured as a programmable hardware element, suchas an FPGA (Field Programmable Gate Array), or as an ASIC (ApplicationSpecific Integrated Circuit), or a combination thereof. Alternatively(or in addition) the processor 404 of the BS 102, in conjunction withone or more of the other components 430, 432, 434, 440, 450, 460, 470may be configured to implement or support implementation of part or allof the features described herein.

In addition, as described herein, processor(s) 404 may be comprised ofone or more processing elements. In other words, one or more processingelements may be included in processor(s) 404. Thus, processor(s) 404 mayinclude one or more integrated circuits (ICs) that are configured toperform the functions of processor(s) 404. In addition, each integratedcircuit may include circuitry (e.g., first circuitry, second circuitry,etc.) configured to perform the functions of processor(s) 404.

Further, as described herein, radio 430 may be comprised of one or moreprocessing elements. In other words, one or more processing elements maybe included in radio 430. Thus, radio 430 may include one or moreintegrated circuits (ICs) that are configured to perform the functionsof radio 430. In addition, each integrated circuit may include circuitry(e.g., first circuitry, second circuitry, etc.) configured to performthe functions of radio 430.

FIG. 5 : Block Diagram of Cellular Communication Circuitry

FIG. 5 illustrates an example simplified block diagram of cellularcommunication circuitry, according to some embodiments. It is noted thatthe block diagram of the cellular communication circuitry of FIG. 5 isonly one example of a possible cellular communication circuit. Accordingto embodiments, cellular communication circuitry 330 may be included ina communication device, such as communication device 106 describedabove. As noted above, communication device 106 may be a user equipment(UE) device, a mobile device or mobile station, a wireless device orwireless station, a desktop computer or computing device, a mobilecomputing device (e.g., a laptop, notebook, or portable computingdevice), a tablet and/or a combination of devices, among other devices.

The cellular communication circuitry 330 may couple (e.g.,communicatively; directly or indirectly) to one or more antennas, suchas antennas 335 a-b and 336 as shown (in FIG. 3 ). In some embodiments,cellular communication circuitry 330 may include dedicated receivechains (including and/or coupled to, e.g., communicatively; directly orindirectly. dedicated processors and/or radios) for multiple RATs (e.g.,a first receive chain for LTE and a second receive chain for 5G NR). Forexample, as shown in FIG. 5 , cellular communication circuitry 330 mayinclude a modem 510 and a modem 520. Modem 510 may be configured forcommunications according to a first RAT, e.g., such as LTE or LTE-A, andmodem 520 may be configured for communications according to a secondRAT, e.g., such as 5G NR.

As shown, modem 510 may include one or more processors 512 and a memory516 in communication with processors 512. Modem 510 may be incommunication with a radio frequency (RF) front end 530. RF front end530 may include circuitry for transmitting and receiving radio signals.For example, RF front end 530 may include receive circuitry (RX) 532 andtransmit circuitry (TX) 534. In some embodiments, receive circuitry 532may be in communication with downlink (DL) front end 550, which mayinclude circuitry for receiving radio signals via antenna 335 a.

Similarly, modem 520 may include one or more processors 522 and a memory526 in communication with processors 522. Modem 520 may be incommunication with an RF front end 540. RF front end 540 may includecircuitry for transmitting and receiving radio signals. For example, RFfront end 540 may include receive circuitry 542 and transmit circuitry544. In some embodiments, receive circuitry 542 may be in communicationwith DL front end 560, which may include circuitry for receiving radiosignals via antenna 335 b.

In some embodiments, a switch 570 may couple transmit circuitry 534 touplink (UL) front end 572. In addition, switch 570 may couple transmitcircuitry 544 to UL front end 572. UL front end 572 may includecircuitry for transmitting radio signals via antenna 336. Thus, whencellular communication circuitry 330 receives instructions to transmitaccording to the first RAT (e.g., as supported via modem 510), switch570 may be switched to a first state that allows modem 510 to transmitsignals according to the first RAT (e.g., via a transmit chain thatincludes transmit circuitry 534 and UL front end 572). Similarly, whencellular communication circuitry 330 receives instructions to transmitaccording to the second RAT (e.g., as supported via modem 520), switch570 may be switched to a second state that allows modem 520 to transmitsignals according to the second RAT (e.g., via a transmit chain thatincludes transmit circuitry 544 and UL front end 572).

As described herein, the modem 510 may include hardware and softwarecomponents for implementing the above features or for switching abandwidth part for a user equipment device and a base station, as wellas the various other techniques described herein. The processors 512 maybe configured to implement part or all of the features described herein,e.g., by executing program instructions stored on a memory medium (e.g.,a non-transitory computer-readable memory medium). Alternatively (or inaddition), processor 512 may be configured as a programmable hardwareelement, such as an FPGA (Field Programmable Gate Array), or as an ASIC(Application Specific Integrated Circuit). Alternatively (or inaddition) the processor 512, in conjunction with one or more of theother components 530, 532, 534, 550, 570, 572, 335 and 336 may beconfigured to implement part or all of the features described herein.

In addition, as described herein, processors 512 may include one or moreprocessing elements. Thus, processors 512 may include one or moreintegrated circuits (ICs) that are configured to perform the functionsof processors 512. In addition, each integrated circuit may includecircuitry (e.g., first circuitry, second circuitry, etc.) configured toperform the functions of processors 512.

As described herein, the modem 520 may include hardware and softwarecomponents for implementing the above features for switching bandwidthparts on a wireless link between a UE and a base station, as well as thevarious other techniques described herein. The processors 522 may beconfigured to implement part or all of the features described herein,e.g., by executing program instructions stored on a memory medium (e.g.,a non-transitory computer-readable memory medium). Alternatively (or inaddition), processor 522 may be configured as a programmable hardwareelement, such as an FPGA (Field Programmable Gate Array), or as an ASIC(Application Specific Integrated Circuit). Alternatively (or inaddition) the processor 522, in conjunction with one or more of theother components 540, 542, 544, 550, 570, 572, 335 and 336 may beconfigured to implement part or all of the features described herein.

In addition, as described herein, processors 522 may include one or moreprocessing elements. Thus, processors 522 may include one or moreintegrated circuits (ICs) that are configured to perform the functionsof processors 522. In addition, each integrated circuit may includecircuitry (e.g., first circuitry, second circuitry, etc.) configured toperform the functions of processors 522.

As described above, in 5G New Radio (NR), a user equipment (UE) can bein one of three states: CONNECTED, INACTIVE, and IDLE. The CONNECTEDstate, referred to herein as the RRC_CONNECTED state, allows for fulldata transmission between the UE and a base station (BS) and the corenetwork (CN). The IDLE stat, referred to herein as the RRC IDLE state,is a power saving state where data is not exchanged. The INACTIVE state,referred to herein as the RRC_INACTIVE state, for a UE is a suspendstate that allows for the UE to return to the CONNECTED state morequickly than if the UE is in the IDLE state. In some embodiments, forthe UE in the inactive state, a UE control plane has a Non-AccessStratum (NAS) connection to the core network (CN). In addition, the UEdoes not have a dedicated Access Stratum (AS) resource and the UE keepsthe Radio Resource Control (RRC) configuration before the UE entersINACTIVE state. Furthermore, in the INACTIVE state in the legacyprocedure, the UE cannot perform any dedicated datatransmission/reception, and if the UE has a dedicated datatransmission/reception, then UE enters CONNECTED state. For DL datatransmission, gNodeB pages the UE via RAN-paging mechanism to trigger UEto enter the CONNECTED state. For UL data transmission, the UE willtrigger a RACH procedure to enter CONNECTED state. In a furtherembodiment, a UE in the INACTIVE state can move within a RNA (e.g., aRAN notification area) without notifying Next Generation-Radio AccessNetwork (NG-RAN). In addition, in this state, the UE in the INACTIVEstate can have the cell selection/re-selection the same as a UE in theRRC IDLE state.

As discussed above, the UE can transition between the different states.For example, a state transition between INACTIVE and CONNECTED statesoccurs with a RRC Control message. For example, when transitioning fromthe CONNECTED state to the INACTIVE sate, a RRC Release withSuspendConfig procedure is used, and when transitioning from theINACTIVE state to the CONNECTED state, a RRC Resume procedure is used.When transitioning between the INACTIVE state and the IDLE state, a RRCRelease procedure may be used.

FIG. 6 is an illustration of some embodiments of a UE 600 switching froman RRC_INACTIVE state to the CONNECTED state using a legacy procedure.In legacy procedure, when the UE 604 is in an RRC_INACTIVE state andwants to transition to the RRC_CONNECTED state, UE 604 sends aRRCResumeRequest 608A to a new gNB 602B. In response to RRCResumeRequest608A, the new gNB 602B find the last serving gNB 602C via the UE'sI-RNTI, and triggers a UE context fetch procedure in which the new gNB602C sends a RETRIEVE UE CONTEXT REQUEST message to last serving gNB602C. The new gNB 602B forwards the MAC-I to the last serving gNB 602Cfor security checking. If the last serving gNB 602C checks the MAC-Isuccessfully, then the last serving gNB 602C provides the UE context tothe new gNB 602B via a RETRIEVE UE CONTEXT RESPONSE message 608C, andthe new gNB 602B decides the target gNB's configuration and sends theRRCResume message to UE 604. As this point, the UE is in theRRC_CONNECTED state.

Once in the RRC_CONNECTED state, UE 604 sends a RRCResumeCompletemessage to the new GNB 602B. Upon receives the RRCResumeCompletemessage, the new gNB 602B trigger the path switch change procedure tothe network (NW) (e.g., data forwarding address indication 608D and pathswitch request 608E) and relocates the UE's anchor node. Otherwise, theUE context fetch procedure fails, and the new gNB 602B send RRCReject orRRCSetup message to UE 604. If data transmission is supported inRRC_INACTIVE state, especially to support the subsequent transmission,the NW behavior for the data transmission to/from core network (CN)needs to be specified.

In some embodiments, even though the transition from INACTIVE to aCONNECTED state takes less time that a transition from an IDLE to aCONNECTED state, the INACTIVE to a CONNECTED state transitions may notidea for many types of data transmissions involving small packettransmissions. In some embodiments, if the UE receives or transmitssmall data transmissions, the amount of time used to transition fromINACTIVE to the CONNECTED state can be large as compared to the timeused for the data transmission. If there a number of small datatransmissions, or a recurring small data transmissions, repeatedlytransitioning from INACTIVE to CONNECTED states can be inefficient. FIG.7A is an illustration of a timeline of a UE switching from an INACTIVEstate to a CONNECTED state. Referring to FIG. 7A, the UE 704A is in anINACTIVE state 710A and receives an indication of a data arrival 714A.The delay for the data transmission 706A is the delay used in order totransition the UE 704A to the CONNECTED state 712A using the RRC Resumeprocedure as described above. Once this procedure is completed, the UE704A is in the CONNECTED state 712A and can proceed with the datatransmission 708A to the network 702A. For small data transmissions,such as a user application keep alive message, an applicationnotification, or other small data transmission to the user plane of theUE 704A, the amount of time to get the UE 704A into the CONNECTED state712A is large in comparison to the time used for the data transmission.Thus, the amount of overhead used for the data transmission is large incomparison to the overall amount of time used for the data transmission.In some embodiments described herein, the time by which such datatransmission occur is reduced.

More specifically, in some embodiments, by allowing data transmissionswhile the UE is in the INACTIVE state, the overhead used to transitionthe UE from the INACTIVE to CONNECTED state is no longer needed. FIG. 7Bis an illustration of a timeline associated with a UE being able tocommunicate data in an INACTIVE state in accordance with someembodiments. Referring to FIG. 7B, the UE 704B is in the INACTIVE state710B when the UE 704B receives an indication of data arrival 714B.Instead of starting a transition to a CONNECTED state, UE, incooperation with one or more gNBs can perform one or more operationsthat allow the UE 714B to communicate the data transmission (e.g.,either transmit or receive the data transmission) while in the INACTIVEstate (710B or 712B). In some embodiments, these operations can have asignificantly smaller delay 706B, which allows the data transmission tooccur in a shorted time than with the legacy procedure depicted in FIG.7A. The different types of operations are described further below.

In some embodiments, the UE transmits data while in the INACTIVE stateby having the last serving gNB remain as an anchor node and having thelast serving gNB receive or transmit the UE data to or from the CN. Foran uplink transmission, when the new gNB receives the data from the UE,the new gNB forwards the data to last serving gNB for forwarding on tothe CN. For a downlink transmission, when last serving gNB receives theUE's data from the CN, the last serving gNB forwards the data to the newgNB and the new gNB transmits to the data to UE. For each of thesetransmissions, the UE remains in the INACTIVE state.

FIG. 8 is an illustration of some embodiments of communicating data witha UE in the INACTIVE state where the last serving gNB remains the anchornode. In some embodiments, for user plane data handling, the L2 protocolstack is split between the new gNB (MAC) and old gNB (RLC, PDCP, SDAP).For a data transfer in the uplink direction, the new gNB derives theDRB's RLC PDU from the received MAC PDU and forwards it to the lastserving gNB via the Xn interface. In some embodiments, for the uplinkdata in the first packet, the new gNB piggybacks the RLC PDU in thecontainer of the UE context request message. Alternatively, the RLC PDUcan be sent together with the UE context request message. Afterreceiving the uplink data, the last serving gNB performs theRLC/PDCP/SDAP operation to decode the received RLC PDU and forwards theupper data (e.g., SDAP SDU) to CN User Plane Function (UPF).

In some embodiments, for a data transfer in the downlink (DL) direction(for both the first and subsequent DL transmissions), the CN/UPFdelivers the packet to the last serving gNB, which performsSDAP/PDCP/RLC handling and assembles the data into RLC PDU. The lastserving gNB then forwards the RLC PDU to the new gNB, which performs theMAC and L1 handling and transmits the data to UE via Uu interface.

Referring to FIG. 8 , a first transmission 806A from the UE 802A to gNB802B occurs while in the INACTIVE state and includes user plane uplinkdata. In response, gNB 802B sends a UE context request message, RETRIEVECONTEXT REQUEST message 806B, with the user plane uplink data, to lastserving gNB 802C. In some embodiments, the user plane uplink data iscontained in the UE context request message. In another embodiment, theuser plane uplink data is sent with the UE context request message butis not contained within it. In some embodiments, the user plane uplinkdata is send as RLC PDU.

In response to UE context request message and the user plane uplinkdata, the last serving gNB 802C forwards the user plane uplink data tothe CN 802D. In some embodiments, the last serving gNB 802C forwards theupper layer (e.g., SDAP SDU) to the CN 802D. In this manner the firstpacket is transferred using a PDU Session Tunnel.

In response to UE context request message and the user plane uplinkdata, the last serving gNB 802C also sends a message back to the new gNB802B with the UE context, for which the new gNB 802B sends anacknowledgement (ACK) regarding the data transfer. In some embodiments,the message is a RETRIEVE CONTEXT RESPONSE message.

Thereafter, both uplink and downlink data transmission by the UE whilein the INACTIVE state occurs with the CN via new gNB 802B, includinghandling the user plane data transferred between the new NB 802B and thelast serving gNB 802C (e.g., UL data 806G, DL data 806J) being RLC PDUand the data transferred between the last serving gNB 802C and the CN(e.g., UL data 806H, DL data 806I) via a PDU Session Tunnel.

In another embodiment, the anchor node is relocated from the lastserving gNB to the new access gNB. Upon receiving the first datatransmission from the UE while in the INACTIVE state, the new gNBperforms a UE context fetch procedure and acquires the UE context fromthe last serving gNB. The new gNB also sends a data forwarding addressindication (e.g., an Xn-U Address Indication) and performs the pathswitch to the CN. At this point, the UE's anchor gNB is updated to thenew access gNB from CN point of view, and the UE's data transmissionto/from the CN is via the new access gNB.

FIG. 9 is an illustration of some embodiments of communicating data witha UE in the inactive state and the new gNB becomes the anchor node. Forthe first packet transmission, the procedure is similar as described inFIG. 8 above, including the same protocol stack split. Referring to FIG.9 , a first transmission 906A from the UE 902A to gNB 902B occurs whilein the INACTIVE state and includes user plane uplink data. In response,gNB 902B sends a UE context request message, RETRIEVE CONTEXT REQUESTmessage 906B, with the user plane uplink data, to last serving gNB 902C.In some embodiments, the user plane uplink data is contained in the UEcontext request message. In another embodiment, the user plane uplinkdata is sent with the UE context request message but is not containedwithin it. In some embodiments, the user plane uplink data is send asRLC PDU.

In response to UE context request message and the user plane uplinkdata, the last serving gNB 902C forwards the user plane uplink data tothe CN 902D. In some embodiments, the last serving gNB 902C forwards theupper layer (e.g., SDAP SDU) to the CN 902D. In this manner the firstpacket is transferred using a PDU Session Tunnel.

In response to UE context request message and the user plane uplinkdata, the last serving gNB 902C also sends a message back to the new gNB902B with the UE context, for which the new gNB 902B sends anacknowledgement (ACK) regarding the data transfer. In some embodiments,the message is a RETRIEVE CONTEXT RESPONSE message.

After receiving the UE context information, the new gNB 902B sends adata forwarding indication (e.g., Xn-U Address Indication 906F) to thelast serving gNB 902C and a Path Switch message 906G to CN 902D. Afterthis occurs, the anchor node is relocated from the last serving gNB 902Cto the new gNB 902B.

For the subsequent transmission, after anchor node relocation, all thedata transmission/reception will be handled by new gNB 902B directly.For example, user plane UL data from UE 902A is transmitted to gNB 902B,which forwards the UL data 906H to CN 902D, while user plane DL datafrom CN 902D is transmitted to gNB 902B, which forwards the DL data 906Ito UE 902A.

In a further embodiment, the new gNB is temporarily assigned as theanchor node for the UE and releases the anchor node responsibility tothe last serving gNB after the transmission has completed. FIG. 10 is anillustration of some embodiments of communicating data with a UE in theINACTIVE state where the new gNB temporarily becomes the anchor node. Insome embodiments, the anchor node is in last serving gNB, but forwardsthe UE context to a new gNB for temporary usage. When new gNB connectsto the last serving gNB, the last serving gNB will provides the INACTIVESMT related UE context (the UE configured for data transmission while inthe INACTIVE state) to the new gNB, and performs the temporary pathswitch to the CN. After the SMT transmission has finished, the new gNBdeletes the UE's context and the temporary path to CN. In this case, theUE's data transmission to/from the CN is via the new access gNB.

Referring to FIG. 10 , for the first packet transmission, the procedureis similar as described in FIG. 8 above, including the same protocolstack split. Referring to FIG. 10 , a first transmission 1006A from theUE 1002A to gNB 1002B occurs while in the INACTIVE state and includesuser plane uplink data. In response, gNB 1002B sends a UE contextrequest message, RETRIEVE CONTEXT REQUEST message 1006B, with the userplane uplink data, to last serving gNB 1002C. In some embodiments, theuser plane uplink data is contained in the UE context request message.In another embodiment, the user plane uplink data is sent with the UEcontext request message but is not contained within it. In someembodiments, the user plane uplink data is send as RLC PDU.

In response to UE context request message and the user plane uplinkdata, the last serving gNB 1002C forwards the user plane uplink data tothe CN 1002D. In some embodiments, the last serving gNB 1002C forwardsthe upper layer (e.g., SDAP SDU) to the CN 1002D. In this manner thefirst packet is transferred using a PDU Session Tunnel.

In response to UE context request message and the user plane uplinkdata, the last serving gNB 1002C also sends a message back to the newgNB 1002B with partial UE context, for which the new gNB 1002B sends anacknowledgement (ACK) regarding the data transfer. In some embodiments,the message is a RETRIEVE CONTEXT RESPONSE message.

After receiving the UE context information, the new gNB 1002B sends adata forwarding indication (e.g., Xn-U Address Indication 1006E) to thelast serving gNB 1002C and a Path Switch message 1006F to CN 1002D.After this occurs, the anchor node is temporality relocated from thelast serving gNB 1002C to the new gNB 1002B.

For the subsequent transmission, after temporary anchor node relocation,all the data transmission/reception will be handled by new gNB 1002Bdirectly. For example, user plane UL data from UE 1002A is transmittedto gNB 1002B, which forwards the UL data 1006G to CN 1002D, while userplane DL data from CN 1002D is transmitted to gNB 1002B, which forwardsthe DL data 1006H to UE 1002A.

FIG. 11A is a flow diagram of one embodiment of a process performed by alast serving gNB for handling a user plane uplink data sent from a UEwhile the UE is in the Radio Resource Control (RRC) inactive(RRC_INACTIVE) state. In some embodiments, the process is performed, atleast in part, by processing logic comprising hardware (e.g., circuitry,dedicated logic, etc.), software (e.g., software running on a chip,software run on a general-purpose computer system or a dedicatedmachine, etc.), firmware, or a combination of the three. In someembodiments, the process is performed by last serving gNB 802C of FIG. 8.

Referring to FIG. 11A, the process begins by processing logic receivingboth a first message requesting UE context and first user plane uplinkdata from a second base station (e.g., a new gNB), where the first userplane uplink data is sent from the UE to the second base station whilethe UE is in the RRC_INACTIVE state (processing block 1101). In someembodiments, the first message is a RETRIEVE UE CONTEXT REQUEST message.In some embodiments, the first user plane uplink data is sent as part ofthe message requesting UE context (e.g., carried in the same container).In another embodiment, the first user plane uplink data is sent togetherwith the message requesting UE context. In some embodiments, the firstuser plane uplink data is sent as an RLC PDU.

In response to receiving both first message requesting UE context andfirst user plane uplink data from a second base station, processinglogic forwards the first user plane uplink data to the core network (CN)(processing block 1102). In some embodiments, the first user planeuplink data is sent to the CN as upper layer data (e.g., SDAP SDU data).

Processing logic also sends a second message to the second base stationin response to the first message (processing block 1103). In someembodiments, the second message comprises a RETRIEVE UE CONTEXT RESPONSEmessage.

Thereafter, processing logic continues operating as an anchor node forthe UE while the UE is in the RRC_INACTIVE state (processing block1104). In some embodiments, the processing logic continues operating asan anchor node by receiving additional user plane uplink data of the UEfrom the second base station transmitted by the UE to the second basestation while the UE was in the RRC_INACTIVE state and forwarding theadditional user plane uplink data to the CN, and/or receiving user planedownlink data for the UE from the CN while the UE was in theRRC_INACTIVE state and forwarding the user plane downlink to the secondbased station for transmission to the UE.

FIG. 11B is a flow diagram of one embodiment of a process performed by anew gNB for handling a user plane uplink data sent from a UE while theUE is in the RRC_INACTIVE state. In some embodiments, the process isperformed, at least in part, by processing logic comprising hardware(e.g., circuitry, dedicated logic, etc.), software (e.g., softwarerunning on a chip, software run on a general-purpose computer system ora dedicated machine, etc.), firmware, or a combination of the three. Insome embodiments, the process is performed by new gNB 802B of FIG. 8 .

Referring to FIG. 11B, the process begins by processing logic receivingfirst user plane uplink data transmitted from a user equipment (UE)while the UE was in the RRC_INACTIVE state (processing block 1121). Insome embodiments, the first user plane uplink data is sent as part ofthe message containing the control information. In another embodiment,the first user plane uplink data is sent together with a messagecontaining the control information. In some embodiments, the first userplane uplink data is sent as an RLC PDU.

In some embodiments, processing logic also receives control informationtransmitted from the UE while the UE was in the RRC_INACTIVE state,along with the first user plane uplink data (processing block 1122). Insome embodiments, the control information includes one or more of an RRCmessage, a UE ID, and MAC-I for security checking and UE identification.

In response to receipt of this information, processing logic sends botha first message to a second base station (e.g., the last serving gNB) torequest UE context and the first user plane uplink data, where the firstuser plane uplink data is for forwarding by the second base station tothe core network (CN) (processing block 1123). In some embodiments, thefirst message is a RETRIEVE UE CONTEXT REQUEST message. In someembodiments, the first user plane uplink data is sent as part of themessage requesting UE context (e.g., carried in the same container). Insome embodiments, the first user plane uplink data is sent as an RLCPDU.

Subsequently, processing logic receives a second message from the secondbase station in response to the first message (processing block 1124).In some embodiments, the second message comprises a RETRIEVE UE CONTEXTRESPONSE message.

After forwarding the first user plane uplink data to the second basestation, processing logic may receive additional user plane uplink datatransmitted from the UE while the UE was in the RRC_INACTIVE state andsends the additional uplink data to the second base station forforwarding to the CN by the second base station (processing block 1125).In some embodiments, the additional user plane uplink data comprise oneor more RLC PDUs.

Also after forwarding the first user plane uplink data to the secondbase station, processing logic may receive user plane downlink data forthe UE from the CN via the second base station while the UE was in theRRC_INACTIVE state, and assembles the user plane downlink data from thesecond base station and transmits the assembled user plane downlink datato the UE as a downlink transmission (processing block 1126). In someembodiments, the user plane downlink data comprise one or more RLC PDUs.

FIG. 12A is a flow diagram of another embodiment of a process performedby a last serving gNB for handling a user plane uplink data sent from aUE while the UE is in the RRC_INACTIVE state. In some embodiments, theprocess is performed, at least in part, by processing logic comprisinghardware (e.g., circuitry, dedicated logic, etc.), software (e.g.,software running on a chip, software run on a general-purpose computersystem or a dedicated machine, etc.), firmware, or a combination of thethree. In some embodiments, the process is performed by last serving gNB902C of FIG. 9 .

Referring to FIG. 12A, the process begins by processing logic receivingboth a first message requesting UE context and first user plane uplinkdata from a second base station (e.g., a new gNB), where the first userplane uplink data is sent from the UE to the second base station whilethe UE is in the RRC_INACTIVE state (processing block 1201). In someembodiments, the first message is a RETRIEVE UE CONTEXT REQUEST message.In some embodiments, the first user plane uplink data is sent as part ofthe message requesting UE context (e.g., carried in the same container).In another embodiment, the first user plane uplink data is sent togetherwith the message requesting UE context. In some embodiments, the firstuser plane uplink data is sent as an RLC PDU.

Processing logic forwards the first user plane uplink data to the corenetwork (CN) (processing block 1202). In some embodiments, the firstuser plane uplink data is sent to the CN as upper layer data (e.g., SDAPSDU data).

Processing logic also sends a second message to the second base stationin response to the first message (processing block 1203) and receives adata forwarding address indication (e.g., Xn-U address indication) fromthe second base station, to enable the second base station to become ananchor node of the UE (processing block 1204). In some embodiments, thesecond message comprises a RETRIEVE UE CONTEXT RESPONSE message.

FIG. 12B is a flow diagram of another embodiment of a process performedby a new gNB for handling a user plane uplink data sent from a UE whilethe UE is in the RRC_INACTIVE state. In some embodiments, the process isperformed, at least in part, by processing logic comprising hardware(e.g., circuitry, dedicated logic, etc.), software (e.g., softwarerunning on a chip, software run on a general-purpose computer system ora dedicated machine, etc.), firmware, or a combination of the three. Insome embodiments, the process is performed by new gNB 902B of FIG. 9 .

Referring to FIG. 12B, the process begins by processing logic receivingfirst user plane uplink data transmitted from a user equipment (UE)while the UE was in the RRC_INACTIVE state (processing block 1221). Insome embodiments, the first user plane uplink data is sent as an RLCPDU.

In some embodiments, processing logic also receives control informationtransmitted from the UE while the UE was in the Radio RRC_INACTIVEstate, along with the first user plane uplink data (processing block1222). In some embodiments, the control information includes one or moreof an RRC message, a UE ID, and MAC-I for security checking and UEidentification.

In response to receiving the information, processing logic sends both afirst message to a second base station (e.g., the last serving gNB) torequest UE context and the first user plane uplink data, where the firstuser plane uplink data is for forwarding by the second base station tothe core network (CN) (processing block 1223). In some embodiments, thefirst message is a RETRIEVE UE CONTEXT REQUEST message. In someembodiments, the first user plane uplink data is sent as part of themessage requesting UE context (e.g., carried in the same container). Inanother embodiment, the first user plane uplink data is sent togetherwith the message requesting UE context. In some embodiments, the firstuser plane uplink data is sent as an RLC PDU.

Subsequently, processing logic receives a second message from the secondbase station in response to the first message (processing block 1224).In some embodiments, the second message comprises a RETRIEVE UE CONTEXTRESPONSE message.

Processing logic also sends a data forwarding address indication (e.g.,an Xn-U address indication) to the second base station (processing block1225) and sends a path switch message to the CN (processing block 1226).

Thereafter, processing logic operates the base station as an anchor nodefor the UE while the UE is in the RRC_INACTIVE state, includingreceiving additional uplink data transmitted by the UE while the UE wasin the RRC_INACTIVE state and forwarding the additional user planeuplink data to the CN, and/or receiving user plane downlink data for theUE from the CN while the UE was in the RRC_INACTIVE state andtransmitting the user plane downlink data to the UE (processing block1227).

FIG. 13A is a flow diagram of yet another embodiment of a processperformed by a last serving gNB for handling a user plane uplink datasent from a UE while the UE is in the RRC_INACTIVE state. In someembodiments, the process is performed, at least in part, by processinglogic comprising hardware (e.g., circuitry, dedicated logic, etc.),software (e.g., software running on a chip, software run on ageneral-purpose computer system or a dedicated machine, etc.), firmware,or a combination of the three. In some embodiments, the process isperformed by last serving gNB 1002C of FIG. 10 .

Referring to FIG. 13A, the process begins by processing logic receivingboth a first message requesting UE context and first user plane uplinkdata from a second base station (e.g., a new gNB), where the first userplane uplink data is sent from the UE to the second base station whilethe UE is in the RRC_INACTIVE state (processing block 1301). In someembodiments, the first message is a RETRIEVE UE CONTEXT REQUEST message.In some embodiments, the first user plane uplink data is sent as part ofthe message requesting UE context (e.g., carried in the same container).In another embodiment, the first user plane uplink data is sent togetherwith the message requesting UE context. In some embodiments, the firstuser plane uplink data is sent as an RLC PDU.

Processing logic forwards the first user plane uplink data to the corenetwork (CN) (processing block 1302). In some embodiments, the firstuser plane uplink data is sent to the CN as upper layer data (e.g., SDAPSDU data).

Processing logic also sends a second message to the second base stationin response to the first message (processing block 1303). In someembodiments, the second message comprises a RETRIEVE UE CONTEXT RESPONSEmessage.

Next, processing logic receives a data forwarding address indication(e.g., Xn-U address indication) from the second base station and ceasesto be an anchor node of the UE (processing block 1304).

Thereafter, data transmission (e.g., uplink user plane data, downlinkuser plane data) between the second base station and the UE occurs whilethe UE is in the RRC_INACTIVE state (processing block 1305).

Subsequently, processing logic receives a transmission completeindication from the second base station, where the transmission completeindication indicates completion of user plane data transmission betweenthe UE and the CN, via the second base station, while the UE is in inthe RRC_INACTIVE state (processing block 1306) and resumes operation asan anchor node for the UE (processing block 1307).

FIG. 13B is a flow diagram of yet another embodiment of a processperformed by a new gNB for handling a user plane uplink data sent from aUE while the UE is in the RRC_INACTIVE state. In some embodiments, theprocess is performed, at least in part, by processing logic comprisinghardware (e.g., circuitry, dedicated logic, etc.), software (e.g.,software running on a chip, software run on a general-purpose computersystem or a dedicated machine, etc.), firmware, or a combination of thethree. In some embodiments, the process is performed by new gNB 1002B ofFIG. 10 .

Referring to FIG. 13B, the process begins by processing logic receivingfirst user plane uplink data transmitted from aUE while the UE was inthe RRC_INACTIVE state (processing block 1321). In some embodiments, thefirst user plane uplink data is sent as part of the message containingthe control information. In another embodiment, the first user planeuplink data is sent together with a message containing the controlinformation. In some embodiments, the first user plane uplink data issent as an RLC PDU.

In some embodiments, processing logic also receives control informationtransmitted from the UE while the UE is in the RRC_INACTIVE state, alongwith the first user plane uplink data (processing block 1322). In someembodiments, the control information includes one or more of an RRCmessage, a UE ID, and MAC-I for security checking and UE identification.

In response to receipt of this information, processing logic sends botha first message to a second base station (e.g., the last serving gNB) torequest UE context and the first user plane uplink data, where the firstuser plane uplink data is for forwarding by the second base station tothe core network (CN) (processing block 1323). In some embodiments, thesecond message comprises a RETRIEVE UE CONTEXT REQUEST message.

Processing logic also receives a second message from the second basestation in response to the first message, where the second messagecontains partial context to enable the second base station to operate asan anchor node for the UE (processing block 1324). In some embodiments,the second message comprises a RETRIEVE UE CONTEXT RESPONSE message.

Processing logic sends a data forwarding address indication (e.g., Xn-Uaddress indication) to the second base station (processing block 1325)and a path switch message to the CN (processing block 1326).

Thereafter, processing logic causes the base station to temporarilyoperate as an anchor node for the UE while the UE is in the RRC_INACTIVEstate, including receiving additional uplink data transmitted by the UEwhile the UE was in the RRC_INACTIVE state and forwarding the additionaluser plane uplink data to the CN, and/or receiving user plane downlinkdata for the UE from the CN while the UE is in the RRC_INACTIVE state,assembling the user plane downlink data from the second base station,and transmitting assembled user plane downlink data to the UE as adownlink transmission (processing block 1327).

Subsequently, processing logic sends a transmission complete indicationto the second base station and ceases operation as an anchor node forthe UE, where the transmission complete indication indicates completionof user plane data transmission between the UE and the CN while the UEis in in the RRC_INACTIVE state (processing block 1328).

In some embodiments described above, the new gNB requests the contextfor the UE in response to receiving an indication of data transmissionfor the UE in the INACTIVE state. In another embodiment, the lastserving gNB sends (e.g., broadcasts) the UE context to potential new gNBprior to a gNB receiving an indication of the data transmission. In thisembodiment, the potential new gNBs are caching the UE context in theevent that the UE is to perform a data transmission with that gNB. Theindication of an upcoming data transmission can be either an ULtransmission from the UE or a DL transmission from the CN.

FIGS. 14A and 14B illustrate some embodiments of communicating data witha UE in the INACTIVE state, where a last served gNB sends a UE contextto another gNB prior to receiving data. Referring to FIG. 14A, the lastserving gNB 1402C sends a RRCRelease with SuspendConfig message 1406A toUE 1402A. The last serving gNB 1402C also sends UE context information1406B to each potential gNB.

Subsequently, UE 1402A transmits user plane uplink data as part oftransmission 1406C to gNB 1402B. In response, gNB 1402B sends a PathSwitch message 1406D to CN 1402D. At this point, the anchor node isrelocated from the last serving gNB 1402 to gNB 1402B. Thereafter,uplink data from UE 1402A is sent to gNB 1402B, which forwards UL data1406F to CN 1402D, and downlink data 1406G from CN 1402D is sent to gNB1402B, which forwards DL data to UE 1402A.

However, the process in FIG. 14A waits once the last serving gNB sendsthe UE context information to potential gNBs until the UE transmits datawhile in the INACTIVE state. However, during this time, if the CN hasdownlink data for the UE prior to the UE transmitting data during theINACTIVE state, the process is FIG. 14B is use to handle the downloaddata transfer.

Referring to FIG. 14B, as with FIG. 14A, the last serving gNB 1422Csends a RRCRelease with SuspendConfig message 1426A to UE 14 s 2A. Thelast serving gNB 14 s 2C also sends UE context information 14 s 6B toeach potential gNB. While waiting for an user plane uplink datatransmission from UE 1422A while in the INACTIVE state, CN 1422D sendsDL data 1426C to the last serving gNB 1422C. In response to DL data1426C, the last serving gNB 1422C sends a paging message 1426D to UE1422A, which the potential gNBs, including dNB 1422B, hears and thensends a paging message 1424A to UE themselves.

Subsequently, in response to the paging message 1424A, UE 1422A performsa data transmission to gNB 1422B while in the INACTIVE state, and inresponse thereto, the anchor changes to gNB 1422B and the new gNB 1422Bsends a data forwarding indication (e.g., Xn-U Address Indication 1426F)to the last serving gNB 1422C and a Path Switch message 14261 to CN1422D. In response to the data forwarding indication (e.g., Xn-U AddressIndication 1426F), the last serving gNB 1422C performs a data forwardingoperation 1426G to forward the DL data 1426C to gNB 1422B for forwardingas DL data 14261 to UE 1422A.

Thereafter, uplink data from UE 1422A is sent to gNB 1422B, whichforwards UL data 1426K to CN 1402D, and downlink data 1426L from CN1422D is sent to gNB 1422B, which forwards DL data to UE 1422A.

FIG. 15A is a flow diagram of another embodiment of a process performedby a last serving gNB for handling sends a UE context to another gNBprior to receiving user plane uplink data from a UE while the UE is inthe RRC_INACTIVE state. In some embodiments, the process is performed,at least in part, by processing logic comprising hardware (e.g.,circuitry, dedicated logic, etc.), software (e.g., software running on achip, software run on a general-purpose computer system or a dedicatedmachine, etc.), firmware, or a combination of the three. In someembodiments, the process is performed by last serving gNB 1402C of FIG.14A.

Referring to FIG. 15A, processing logic sends a first message to the UEto configure the UE in a Radio Resource Control (RRC) inactive(RRC_INACTIVE) state (processing block 1501). In some embodiments, thefirst message comprises a Radio Resource Control (RRC) Release withSuspend Configuration (SuspendConfig) message.

Processing logic also sends the UE context to one or more other basestations that can potentially act as the new base station for the UE(processing block 1502). At this point, the UE may send uplink userplane data to a new gNB while the UE is in the RRC_INACTIVE state.

At times, new downlink data from the CN may be sent to the last servinggNB prior to the UE sending data to the new gNB while the UE is in theRRC_INACTIVE state. FIG. 15B is a flow diagram of one embodiment of aprocess for handling new downlink data from the CN that is sent to thelast serving gNB prior to the UE sending data to the new gNB while theUE is in the RRC_INACTIVE state. In some embodiments, the process isperformed, at least in part, by processing logic comprising hardware(e.g., circuitry, dedicated logic, etc.), software (e.g., softwarerunning on a chip, software run on a general-purpose computer system ora dedicated machine, etc.), firmware, or a combination of the three. Insome embodiments, the process is performed by last serving gNB 1422C ofFIG. 14B.

Referring to FIG. 15B, processing logic sends a first message to the UEto configure the UE in a Radio Resource Control (RRC) inactive(RRC_INACTIVE) state (processing block 1521). In some embodiments, thefirst message comprises a Radio Resource Control (RRC) Release withSuspend Configuration (SuspendConfig) message.

Processing logic also sends the UE context to one or more other basestations that can potentially act as the new base station for the UE(processing block 1522).

Then, processing logic receives a transmission from the CN with downlinkdata for the UE while the UE is in the RRC_INACTIVE state (processingblock 1523).

In response to the downlink data, processing logic pages nearby gNBs(e.g., gNBs within range) to notify the UE of a downlink transmission(processing block 1524). At this point, that potential new gNBs for theUE that received the page, in turn, page the UE.

Subsequently, processing logic receives a data forwarding addressindication (e.g., Xn-U address indication) from a second base station(e.g., a new gNB) in response to a first data transmission from the UEto the second base station while the UE is in the RRC_INACTIVE state,where the second base station is one of the one or more other basestations to which the first base station sent the UE context and becomesthe anchor node for the UE (processing block 1525).

In response to receiving the data forwarding address indication,processing logic forwards the downlink data to the second base stationfor forwarding to the UE (processing block 1526).

FIG. 16A is a flow diagram of yet another embodiment of a processperformed by a last serving gNB for handling sends a UE context toanother gNB prior to receiving user plane uplink data from a UE whilethe UE is in the RRC_INACTIVE state. In some embodiments, the process isperformed, at least in part, by processing logic comprising hardware(e.g., circuitry, dedicated logic, etc.), software (e.g., softwarerunning on a chip, software run on a general-purpose computer system ora dedicated machine, etc.), firmware, or a combination of the three. Insome embodiments, the process is performed by new gNB 1402B of FIG. 14A.

Referring to FIG. 16A, the process begins by processing logic receivinga UE context that a second base station (e.g., a last serving gNB) sentto one or more other base stations that can potentially act as the newbase station for a UE (processing block 1601).

Processing logic also receives first user plane uplink data transmittedfrom the UE while the UE is in the RRC_INACTIVE state (processing block1602).

In response, processing logic sends a path switch message to the corenetwork (CN) (processing block 1603) and thereafter operates as ananchor node for the UE, which may include receiving additional uplinkdata transmitted by the UE while the UE is in the RRC_INACTIVE state andforwarding the additional user plane uplink data to the CN, and/or mayinclude receiving user plane downlink data for the UE from the CN whilethe UE is in the RRC_INACTIVE state and transmitting the user planedownlink to the UE (processing block 1604).

FIG. 16B is a flow diagram of another embodiment of a process forhandling new downlink data from the CN that is sent to the last servinggNB prior to the UE sending data to the new gNB while the UE is in theRRC_INACTIVE state. In some embodiments, the process is performed, atleast in part, by processing logic comprising hardware (e.g., circuitry,dedicated logic, etc.), software (e.g., software running on a chip,software run on a general-purpose computer system or a dedicatedmachine, etc.), firmware, or a combination of the three. In someembodiments, the process is performed by last serving gNB 1422C of FIG.14B.

Referring to FIG. 16B, the process begins by processing logic receivinga UE context that a second base station (e.g., a last serving gNB) sendsto one or more other base stations that can potentially act as the newbase station for a UE (processing block 1621).

Next, processing logic receives a paging message from the second basestation indicating that a transmission from CN with downlink data hasoccurred while the UE is in the RRC_INACTIVE state (processing block1622) and, in response thereto, pages the UE to notify the UE of adownlink transmission (processing block 1623).

Subsequently, processing logic receives first user plane uplink datatransmitted from the UE while the UE is in the RRC_INACTIVE state andthereafter operates as an anchor node for the UE in response toreceiving the first user plane uplink data from the UE (processing block1624).

Processing logic sends a data forwarding address indication (e.g., Xn-Uaddress indication) to the second base station after receiving the firstuser plane uplink data transmitted from the UE while the UE is in theRRC_INACTIVE state (processing block 1625).

Processing logic receives the downlink data from the second base stationwhile the UE is in the RRC_INACTIVE state (processing block 1626), sendsa path switch message to the core network (CN) and operates as an anchornode for the UE (processing block 1627), and transmits the downlink datato the UE (processing block 1628).

Thereafter, processing logic receives additional uplink data transmittedby the UE while the UE is in the RRC_INACTIVE state and forward theadditional user plane uplink data to the CN, and/or receive user planedownlink data for the UE from the CN while the UE is in the RRC_INACTIVEstate and transmit the user plane downlink to the UE (processing block1629).

Portions of what was described above may be implemented with logiccircuitry such as a dedicated logic circuit or with a microcontroller orother form of processing core that executes program code instructions.Thus processes taught by the discussion above may be performed withprogram code such as machine-executable instructions that cause amachine that executes these instructions to perform certain functions.In this context, a “machine” may be a machine that converts intermediateform (or “abstract”) instructions into processor specific instructions(e.g., an abstract execution environment such as a “virtual machine”(e.g., a Java Virtual Machine), an interpreter, a Common LanguageRuntime, a high-level language virtual machine, etc.), and/or,electronic circuitry disposed on a semiconductor chip (e.g., “logiccircuitry” implemented with transistors) designed to executeinstructions such as a general-purpose processor and/or aspecial-purpose processor. Processes taught by the discussion above mayalso be performed by (in the alternative to a machine or in combinationwith a machine) electronic circuitry designed to perform the processes(or a portion thereof) without the execution of program code.

The present invention also relates to an apparatus for performing theoperations described herein. This apparatus may be specially constructedfor the required purpose, or it may comprise a general-purpose computerselectively activated or reconfigured by a computer program stored inthe computer. Such a computer program may be stored in a computerreadable storage medium, such as, but is not limited to, any type ofdisk including floppy disks, optical disks, CD-ROMs, andmagnetic-optical disks, read-only memories (ROMs), RAMs, EPROMs,EEPROMs, magnetic or optical cards, or any type of media suitable forstoring electronic instructions, and each coupled to a computer systembus.

A machine readable medium includes any mechanism for storing ortransmitting information in a form readable by a machine (e.g., acomputer). For example, a machine readable medium includes read onlymemory (“ROM”); random access memory (“RAM”); magnetic disk storagemedia; optical storage media; flash memory devices; etc.

An article of manufacture may be used to store program code. An articleof manufacture that stores program code may be embodied as, but is notlimited to, one or more memories (e.g., one or more flash memories,random access memories (static, dynamic or other)), optical disks,CD-ROMs, DVD ROMs, EPROMs, EEPROMs, magnetic or optical cards or othertype of machine-readable media suitable for storing electronicinstructions. Program code may also be downloaded from a remote computer(e.g., a server) to a requesting computer (e.g., a client) by way ofdata signals embodied in a propagation medium (e.g., via a communicationlink (e.g., a network connection)).

The preceding detailed descriptions are presented in terms of algorithmsand symbolic representations of operations on data bits within acomputer memory. These algorithmic descriptions and representations arethe tools used by those skilled in the data processing arts to mosteffectively convey the substance of their work to others skilled in theart. An algorithm is here, and generally, conceived to be aself-consistent sequence of operations leading to a desired result. Theoperations are those requiring physical manipulations of physicalquantities. Usually, though not necessarily, these quantities take theform of electrical or magnetic signals capable of being stored,transferred, combined, compared, and otherwise manipulated. It hasproven convenient at times, principally for reasons of common usage, torefer to these signals as bits, values, elements, symbols, characters,terms, numbers, or the like.

It should be kept in mind, however, that all of these and similar termsare to be associated with the appropriate physical quantities and aremerely convenient labels applied to these quantities. Unlessspecifically stated otherwise as apparent from the above discussion, itis appreciated that throughout the description, discussions utilizingterms such as “sending,” “receiving,” “switching,” “receiving,”“communicating,” “transmitting,” “aggregating,” “monitoring,”“removing,” or the like, refer to the action and processes of a computersystem, or similar electronic computing device, that manipulates andtransforms data represented as physical (electronic) quantities withinthe computer system's registers and memories into other data similarlyrepresented as physical quantities within the computer system memoriesor registers or other such information storage, transmission or displaydevices.

The processes and displays presented herein are not inherently relatedto any particular computer or other apparatus. Various general-purposesystems may be used with programs in accordance with the teachingsherein, or it may prove convenient to construct a more specializedapparatus to perform the operations described. The required structurefor a variety of these systems will be evident from the descriptionbelow. In addition, the present invention is not described withreference to any particular programming language. It will be appreciatedthat a variety of programming languages may be used to implement theteachings of the invention as described herein.

It is well understood that the use of personally identifiableinformation should follow privacy policies and practices that aregenerally recognized as meeting or exceeding industry or governmentalrequirements for maintaining the privacy of users. In particular,personally identifiable information data should be managed and handledso as to minimize risks of unintentional or unauthorized access or use,and the nature of authorized use should be clearly indicated to users.

The foregoing discussion merely describes some exemplary embodiments ofthe present invention. One skilled in the art will readily recognizefrom such discussion, the accompanying drawings and the claims thatvarious modifications can be made without departing from the spirit andscope of the invention.

What is claimed is:
 1. A method for operating a first base station of acommunication system, the first base station being a last serving basestation for a user equipment (UE) and acting an anchor node for the UEbefore the UE enters a Radio Resource Control (RRC) inactive(RRC_INACTIVE) state, the method comprising: receiving, by the firstbase station, first user plane uplink data and a first messagerequesting UE context from a second base station, the first user planeuplink data being sent from the UE to the second base station while theUE is in the RRC_INACTIVE state; forwarding, by the first base station,the first user plane uplink data to a core network (CN) of thecommunication system; sending, by the first base station to the secondbase station, a second message containing UE context information inresponse to the first message; and continuing to operate the first basestation as the anchor node for the UE by transferring additional userplane data between the second base station and the CN while the UE is inthe RRC_INACTIVE state.
 2. The first base station of claim 1, whereinthe first user plane uplink data is in the first message.
 3. The firstbase station of claim 1, wherein the first user plane uplink data istransmitted with the first message but outside of the first message. 4.The first base station of claim 1, wherein the first user plane uplinkdata is received by the first base station from the second base stationas a Radio Link Control Packet Data Unit (RLC PDU), and whereincontinuing to operate the first base station as the anchor node for theUE comprises: decoding, by the first base station, the received RLC PDUusing Convergence Protocol (PDCP) and Service Data Adaptation Protocol(SDAP) operations.
 5. The first base station of claim 1, whereincontinuing to operate the first base station as the anchor node for theUE comprises: receiving, by the first base station from the second basestation, additional user plane uplink data sent from the UE to thesecond base station while the UE is in the RRC_INACTIVE state; andforwarding the additional user plane uplink data by the first basestation to the CN via a Packet Data Unit (PDU) Session Tunnel.
 6. Thefirst base station of claim 5, wherein the first user plane uplink dataand the additional user plane uplink data are received by the first basestation from the second base station as one or more Radio Link Control(RLC) PDUs, and wherein the first user plane uplink data and theadditional user plane uplink data are forwarded by the first station tothe CN as Service Data Adaptation Protocol service data unit (SDAP SDU)data.
 7. The first base station of claim 1, wherein continuing tooperate the first base station as the anchor node for the UE comprises:receiving, by the first base station from the CN, user plane downlinkdata for the UE while the UE is in the RRC_INACTIVE state; andforwarding the user plane downlink data by the first base station to thesecond based station for transmission to the UE.
 8. The first basestation of claim 7, wherein the user plane downlink data are forwardedby the first base station to the second base station as one or moreRadio Link Control Packet Data Units (RLC PDUs).
 9. A method foroperating a first base station of a communication system, the methodcomprising: receiving, by the first base station from a user equipment(UE), first user plane uplink data while the UE is in the Radio ResourceControl (RRC) inactive (RRC_INACTIVE) state; sending, by the first basestation, the first user plane uplink data and a first message requestingUE context to a second base station for the second base station toforward the first user plane uplink data to a core network (CN) of thecommunication system, the second base station operating as an anchornode for the UE before the UE enters the RRC_INACTIVE state; receiving,by the first base station from the second base station, a second messagecontaining UE context information in response to the first message; andtransferring, by the first base station, additional user plane databetween the UE and the CN via the second base station while the UE is inthe RRC_INACTIVE state.
 10. The first base station of claim 9, whereinthe first user plane uplink data is in the first message.
 11. The firstbase station of claim 9, wherein the first user plane uplink data istransmitted with the first message but outside of the first message. 12.The first base station of claim 9, wherein the method further comprises:receiving, by the first base station from the UE, control informationcomprising one or more of a Radio Resource Control (RRC) message, a UEID, and information used to perform security check on the UE.
 13. Thefirst base station of claim 9, wherein the first user plane uplink datais sent by the first base station to the second base station as a RadioLink Control Packet Data Unit (RLC PDU).
 14. The first base station ofclaim 9, wherein transferring by the first base station additional userplane data between the UE and the CN via the second base stationcomprises: receiving, by the first base station from the UE, additionaluser plane uplink data while the UE is in the RRC_INACTIVE state; andsending, by the first base station, the additional user plane uplinkdata to the second base station for the second base station to forwardto the CN.
 15. The first base station of claim 14, wherein theadditional user plane uplink data are sent by the first base station tothe second base station as one or more Radio Link Control Packet DataUnit (RLC PDU).
 16. The first base station of claim 9, whereintransferring by the first base station additional user plane databetween the UE and the CN via the second base station comprises:receiving, by the first base station, user plane downlink data for theUE forwarded by the second base station from the CN; assembling, by thefirst base station, the user plane downlink data; and transmitting, bythe first base station, assembled user plane downlink data to the UE.17. The first base station of claim 16, wherein the user plane downlinkdata for the UE is received by the first base station from the secondbase station as one or more Radio Link Control Packet Data Unit (RLCPDU).
 18. The first base station of claim 9, wherein the method furthercomprises: continuing to operate the second base station as the anchornode for the UE while the UE is in the RRC_INACTIVE state.
 19. A firstbase station of a communication system, the first base station being alast serving base station for a user equipment (UE) and acting as ananchor node for the UE before the UE enters a Radio Resource Control(RRC) inactive (RRC_INACTIVE) state, the first base station comprising:a processor; and a memory coupled to the processor to storeinstructions, which when executed by the processor cause the processorto: receive first user plane uplink data and a first message requestingUE context from a second base station, the first user plane uplink databeing sent from the UE to the second base station while the UE is in theRRC_INACTIVE state; forward the first user plane uplink data to a corenetwork (CN) of the communication system; send a second messagecontaining UE context information to the second base station in responseto the first message; and continue to operate the first base station asthe anchor node for the UE by the first base station being configured totransfer additional user plane data between the second base station andthe CN while the UE is in the RRC_INACTIVE state.
 20. A first basestation of a communication system, comprising: a processor; and a memorycoupled to the processor to store instructions, which when executed bythe processor cause the processor to: receive first user plane uplinkdata transmitted from a user equipment (UE) while the UE is in the RadioResource Control (RRC) inactive (RRC_INACTIVE) state; send the firstuser plane uplink data and a first message requesting UE context to asecond base station for the second base station to forward the firstuser plane uplink data to a core network (CN) of the communicationsystem, the second base station operating as an anchor node for the UEbefore the UE enters the RRC_INACTIVE state; receive a second messagecontaining UE context information from the second base station inresponse to the first message; and transfer additional user plane databetween the UE and the CN via the second base station while the UE is inthe RRC_INACTIVE state.